Re: [patch 1/3] Trace code and documentation

Randy Dunlap
2007-09-26T18:41:48Z

On Wed, 26 Sep 2007 11:22:35 -0700 David J. Wilder wrote:

> diff --git a/Documentation/trace.txt b/Documentation/trace.txt
> new file mode 100644
> index 0000000..0e42fb8
> --- /dev/null
> +++ b/Documentation/trace.txt
> @@ -0,0 +1,160 @@
> +Trace User Interface
> +===================
> +When a trace channel is created and started, the following
> +directories and files are created in the root of the mounted debugfs.
> +
> +/debug (root of the debugfs)
> + /<trace-root-dir>
> + /<trace-name>
> + trace0...traceN-1 Per-CPU trace data, one
> + file per CPU.
> +
> + state Start or stop tracing by
> + by writing the strings
> + "start" or "stop" to this
> + file. Read the file to get the
> + current state.
> +
> + dropped The number of records dropped
> + due to a full-buffer condition,
> + for non-TRACE_FLIGHT_CHANNELs
> + only.
> +
> + rewind Trigger a rewind by writing
> + to this file. i.e. start
> + next read at the beginning
> + again. Only available for
> + TRACE_FLIGHT_CHANNELS.
> +
> +
> + nr_sub Number of sub-buffers
> + in the channel.
> +
> + sub_size Size of sub-buffers in
> + the channnel.
> +
> +Trace data is gathered from the trace[0...N] files using one of the
> +available interfaces provided by relay.

For your next patchset (whenever that is), above should be
trace[0...N-1] files

> +When using the read(2) interface, as data is read it is marked as
> +consumed by the relay subsystem. Therefore, subsequent reads will
> +only return unconsumed data.

---
~Randy
Phaedrus says that Quality is about caring.